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In loquat, apex of a current shoot changes from vegetative to reproductive stage during summer, i.e. under high temperature conditions. Indeed, just before floral bud differentiation, a decline in the growth rate due to high temperature takes place. The aim of this work is to study the role of this 'summer rest period' on the apex transition from vegetative to reproductive stage. For this purpose 1) sprouting of secondary shoots was promoted at different times, removing the main shoot, before, during and after floral bud differentiation occurred and 2) groups of trees were shifted to a greenhouse under average maximum temperature not exceeding 25 ° C during different periods from June to October. Floral bud differentiation was evaluated. LEAFY (LFY), APETALA (AP1), TERMINAL FLOWERING 1 (TFL1) and FLOWERING LOCUS T (FT1) expression and hormonal content in abscisic acid (ABA), gibberellins (GAs), indoleacetic acid (IAA) and cytokinins (CKs) were analyzed in bud collected during the summer. Results suggest that the date of shoot apex removal determining floral bud differentiation of new shoots, so that the percentage of the new reproductive shoots reduced with the delaying of apex removal. On the other hand, maximum average temperature not exceeding 25 ° C prevented floral bud differentiation. Buds of the trees under indoors conditons displayed lower expression of identity floral genes EjLFY and EjAP1 than buds of trees grown in field. On the contrary, the floral repressor EjTFL1 and EjFT1 gene expressed higher in buds of the trees grown indoors. Time-course of ABA decreased in buds of trees grown in field during studied period while in buds of trees under greenhouse conditions displayed a growing trend. Time-course of GAs, IAA and CKs concentrations did not show remarkable differences between buds of trees growing under field and indoors conditions. Accordingly, 1) secondary shoots emerged from mid- August are unfitness to flower and 2) maximum average tempertature 25±1 °C during the summer prevents floral bud differentiation, enhances ABA biosynthesis, reduces EjLFY and EjAP1 expression and enhance EjTFL1 expression in the apex. / El níspero japonés diferencia sus yemas durante el verano, después de un periodo de ralentización del crecimiento vegetativo ligado a las altas temperaturas que se conoce como reposo estival. El objetivo de esta tesis fue estudiar la influencia de la parada estival en la diferenciación floral de esta especie. Para ello se diseñó un experimento en el que se forzó la brotación de brotes anticipados eliminado el ápice principal en diferentes fechas entre julio y septiembre, antes, durante y después de la parada estival. Paralelamente se diseñó otro experimento en el que se cambiaron las condiciones climáticas a grupos de árboles manteniéndolos en un invernadero a una temperatura máxima media de 25 °C durante diferentes periodos de diversa duración. Se evaluó la diferenciación floral y se analizó la expresión de los genes relacionados con la floración LEAFY (LFY), APETALA (AP1), TERMINAL FLOWERING 1 (TFL1) and FLOWERING LOCUS T (FT1) y el contenido hormonal en ácido abscisico (ABA), giberelinas (GAs), ácido indolácetico (AIA) y citoquininas (CKs) en yemas terminales muestreadas a lo largo del verano. Los resultados indican que la fecha de brotación modifica la diferenciación floral de los brotes anticipados siendo el porcentaje de brotes reproductivos inversamente proporcional a la fecha de eliminación del meristemo. Del mismo modo unas condiciones de temperatura máxima no superior a 25 °C impidieron la diferenciación floral. Las yemas de los árboles que estuvieron bajo dichas condiciones mantuvieron unos niveles de expresión de los genes de identidad floral, EjLFY y EjAP1, mucho menor que la de los árboles en condiciones de campo. Por el contrario, la expresión del represor EjTFL1 y del gen EjFT1 fue mayor en los árboles en invernadero. Por otro lado, el contenido endógeno de ABA descendió en los árboles situados en el campo durante el periodo de estudio mientras que en los árboles situados en el invernadero tuvo una evolución ascendente. Las concentraciones de GAs, AIA y CKs no mostraron prácticamente diferencias entre los ápices de los árboles mantenidos en campo y en invernadero. De acuerdo con ello, 1) los brotes anticipados surgidos a partir de mitad de agosto son incapaces de florecer y 2) la ausencia de altas temperaturas del verano promueve la acumulación de ABA, aumenta la expresión del gen represor (EjTFL1) y reduce la expresión de los genes de identidad floral (EjLFY y EjAP1) en yemas de níspero impidiendo su diferenciación floral. / El nispro japonés diferència les seus gemmes durant l'estiu, després d'un període d'alentiment del creixement vegetatiu lligat a les altes temperatures que es coneix com repòs estival. L'objectiu d'aquesta Tesi va ser estudiar la influència de la parada estival en la diferenciació floral d'aquesta espècie. Per a això es va dissenyar un experiment en què es va forçar la aparició dels brots anticipats eliminat l'àpex principal en diferents dates entre juliol i setembre, abans, durant i després de l'aturada estival. Paral·lelament es va dissenyar un altre experiment en què es van canviar les condicions climàtiques a grups d'arbres mantenint-los en un hivernacle a una temperatura màxima mitjana de 25 °C durant diferents períodes de diversa durada. Es va avaluar la diferenciació floral i es va analitzar l'expressió dels gens relacionats amb la floració LEAFY (LFY), APETALA (AP1), TERMINAL FLOWERING 1 (TFL1) and FLOWERING LOCUS T (FT1) i el contingut hormonal en àcid abscísic (ABA) , gibberel·lines (GAs), àcid indolacètic (AIA) i citoquinines (CKs) en gemmes terminals mostrejades al llarg de l'estiu. Els resultats indiquen que la data de brotació modifica la diferenciació floral dels brots anticipats i el percentatge de brots reproductius es inversament proporcional a la data d'eliminació del meristema. De la mateixa manera unes condicions de temperatura màxima no superior a 25 ° C varen impedir la diferenciació floral. Les gemmes dels arbres que van estar sota aquestes condicions van mantenir uns nivells d'expressió dels gens d'identitat floral, EjLFY i EjAP1, molt menor que la dels arbres en condicions de camp. Per contra, l'expressió del repressor EjTFL1 i del gen EjFT1 va ser més gran en els arbres en hivernacle. D'altra banda, el contingut endogen d'ABA va baixar en els arbres situats al camp durant el període d'estudi mentre que en els arbres situats a l'hivernacle va tenir una evolució ascendent. Les concentracions de GAs, AIA i CKS no van mostrar pràcticament diferències entre els àpexs dels arbres mantinguts en camp i en hivernacle. D'acord amb això, 1) els brots anticipats sorgits a partir de meitat d'agost són incapaços de florir i 2) l'absència d'altes temperatures de l'estiu promou l'acumulació d'ABA, augmenta l'expressió del gen repressor (EjTFL1) i redueix l'expressió dels gens d'identitat floral (EjLFY i EjAP1) en gemmes de nispro del Japó impedint la seva diferenciació floral. / García Lorca, AL. (2017). Temperature regulating floral bud differentiation in loquat (Eriobotrya japonica Lindl.). Hormonal and genetic aspects [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/79873

O hábito de crescimento influencia o balanço entre o desenvolvimento vegetativo e o reprodutivo das plantas. Este, por sua vez, está diretamente vinculado a diversas variáveis de interesse agronômico, como produtividade e consumo de água. Em tomateiro, existem três hábitos de crescimento conhecidos: determinado, indeterminado e semi-determinado, sendo esse último na verdade determinado, porém com uma extensão do ciclo vegetativo. Cultivares de crescimento determinado são largamente utilizadas para produção de tomates destinados à indústria (molhos e ketchups), e as indeterminadas destinadas ao consumo in natura. Por outro lado, genótipos de crescimento semi-determinado, embora ainda sejam pouco explorados, apresentam-se como ótimas opções tanto para indústria quanto para o consumo in natura. Diante disto, o presente trabalho teve por objetivo avaliar a implicação do hábito de crescimento semi-determinado no desempenho produtivo e na eficiência no uso da água de plantas de tomateiro. Para tal, genótipos com diferentes hábitos de crescimento foram produzidos, por meio de introgressões de variações alélicas que afetam o hábito de crescimento das plantas, no background genético da cultivar miniatura de tomateiro Micro-Tom (MT). A caracterização desses genótipos demonstrou que os materiais de crescimento semideterminado apresentam um atraso no florescimento, emitindo em média uma folha a mais antes da formação da primeira inflorescência. Além disso, verificasse que essas plantas apresentam uma altura intermediária entre genótipos de crescimento determinado e indeterminado, aos 50 dias após a semeadura. Já para características agronômicas, constatou-se um aumento significativo na produtividade e no conteúdo de sólidos solúveis totais (brix) nos frutos dos genótipos de crescimento semi-determinado em comparação com o de crescimento determinado. Os dados sugerem que esse efeito seja resultante de um balanço mais equilibrado entre o desenvolvimento vegetativo e o reprodutivo, evidenciado pela ausência de diferença significativa na partição de massa seca oriunda do desenvolvimento vegetativo e do reprodutivo nesses genótipos, quando comparados aos genótipos de crescimento determinado e indeterminado. A eficiência no uso da água (EUA) foi avaliada tanto gravimetricamente (massa seca total produzida por quantidade de água transpirada), quanto através de discriminação isotópica. Os genótipos de crescimento semi-determinado apresentaram maior EUA do que os genótipos determinado e indeterminado aos 50 dias após a semeadura. Curiosamente, as plantas de crescimento semi-determinado mostraram-se mais resistentes, quando submetidas a um estresse de seca, que o genótipo de crescimento determinado utilizado como controle nas avaliações. Entretanto, são necessários estudos para elucidar o mecanismo envolvido nesta resistência. Em conclusão, os resultados aqui apresentados sugerem que os genótipos de crescimento semi-determinado atingiram o balanço ótimo entre desenvolvimento vegetativo e reprodutivo, de forma a aumentar concomitantemente, produtividade, conteúdo de brix nos frutos, e eficiência no uso da água. / Growth habit influences the balance between vegetative and reproductive development of plants. This, in turn, is directly linked to several variables of agronomic interest, such as yield and water-use efficiency (WUE). In tomato, there are three growth habits: determinate, indeterminate and semi-determinate, the latter being actually determinate, but with an extension of the vegetative cycle. Cultivars of determinate growth are widely used for processing-tomato industry (sauces and ketchups), and indeterminate for in natura consumption (production to salads). On the other hand, semi-determinate growth genotypes, although are still poorly explored, they present an excellent option for both the industry and in natura consumption. Thus, the aim of the present study was to evaluate the implication of the semi-determinate growth habit in productive performance and in WUE of tomato plants. For this reason, genotypes with different growth habits were produced through introgression of allelic variations that affect the plants growth habit, in the genetic background of the tomato cultivar Micro-Tom (MT). The characterization of these genotypes showed that the semi-determinate growth materials exhibit a delay in flowering, producing on average one extra leaf before the first inflorescence formation. In addition, this architecture presents an intermediate height between determinate and indeterminate growth genotypes, 50 days after sowing. As for agronomic traits, we found a significant increase in yield and total soluble solids content (brix) in the fruits of semi-determinate growth genotypes compared with determinate growth. Our data suggest this effect is resulting from a more balanced vegetative and reproductive development, evidenced by the absence of significant difference on the dry matter partition derived from the vegetative and reproductive development in these genotypes, when compared to determinate and indeterminate growth genotypes. WUE was evaluated both gravimetrically (dry mass produced per amount of water transpired), and through isotopic discrimination. The semideterminate growth genotypes showed higher WUE than determinate and indeterminate genotypes at 50 days after sowing. Interestingly, the plants of semideterminate growth were more resistant than determinate growth genotype used as control, when exposed to drought stress. However, studies are needed to elucidate the mechanism involved in this resistance. In conclusion, the results presented here suggest that the genotypes of semi-determinate growth reached the optimal balance between vegetative and reproductive development, in order to increase concomitantly, productivity, brix content in the fruits, and WUE.

O hábito de crescimento influencia o balanço entre o desenvolvimento vegetativo e o reprodutivo das plantas. Este, por sua vez, está diretamente vinculado a diversas variáveis de interesse agronômico, como produtividade e consumo de água. Em tomateiro, existem três hábitos de crescimento conhecidos: determinado, indeterminado e semi-determinado, sendo esse último na verdade determinado, porém com uma extensão do ciclo vegetativo. Cultivares de crescimento determinado são largamente utilizadas para produção de tomates destinados à indústria (molhos e ketchups), e as indeterminadas destinadas ao consumo in natura. Por outro lado, genótipos de crescimento semi-determinado, embora ainda sejam pouco explorados, apresentam-se como ótimas opções tanto para indústria quanto para o consumo in natura. Diante disto, o presente trabalho teve por objetivo avaliar a implicação do hábito de crescimento semi-determinado no desempenho produtivo e na eficiência no uso da água de plantas de tomateiro. Para tal, genótipos com diferentes hábitos de crescimento foram produzidos, por meio de introgressões de variações alélicas que afetam o hábito de crescimento das plantas, no background genético da cultivar miniatura de tomateiro Micro-Tom (MT). A caracterização desses genótipos demonstrou que os materiais de crescimento semideterminado apresentam um atraso no florescimento, emitindo em média uma folha a mais antes da formação da primeira inflorescência. Além disso, verificasse que essas plantas apresentam uma altura intermediária entre genótipos de crescimento determinado e indeterminado, aos 50 dias após a semeadura. Já para características agronômicas, constatou-se um aumento significativo na produtividade e no conteúdo de sólidos solúveis totais (brix) nos frutos dos genótipos de crescimento semi-determinado em comparação com o de crescimento determinado. Os dados sugerem que esse efeito seja resultante de um balanço mais equilibrado entre o desenvolvimento vegetativo e o reprodutivo, evidenciado pela ausência de diferença significativa na partição de massa seca oriunda do desenvolvimento vegetativo e do reprodutivo nesses genótipos, quando comparados aos genótipos de crescimento determinado e indeterminado. A eficiência no uso da água (EUA) foi avaliada tanto gravimetricamente (massa seca total produzida por quantidade de água transpirada), quanto através de discriminação isotópica. Os genótipos de crescimento semi-determinado apresentaram maior EUA do que os genótipos determinado e indeterminado aos 50 dias após a semeadura. Curiosamente, as plantas de crescimento semi-determinado mostraram-se mais resistentes, quando submetidas a um estresse de seca, que o genótipo de crescimento determinado utilizado como controle nas avaliações. Entretanto, são necessários estudos para elucidar o mecanismo envolvido nesta resistência. Em conclusão, os resultados aqui apresentados sugerem que os genótipos de crescimento semi-determinado atingiram o balanço ótimo entre desenvolvimento vegetativo e reprodutivo, de forma a aumentar concomitantemente, produtividade, conteúdo de brix nos frutos, e eficiência no uso da água. / Growth habit influences the balance between vegetative and reproductive development of plants. This, in turn, is directly linked to several variables of agronomic interest, such as yield and water-use efficiency (WUE). In tomato, there are three growth habits: determinate, indeterminate and semi-determinate, the latter being actually determinate, but with an extension of the vegetative cycle. Cultivars of determinate growth are widely used for processing-tomato industry (sauces and ketchups), and indeterminate for in natura consumption (production to salads). On the other hand, semi-determinate growth genotypes, although are still poorly explored, they present an excellent option for both the industry and in natura consumption. Thus, the aim of the present study was to evaluate the implication of the semi-determinate growth habit in productive performance and in WUE of tomato plants. For this reason, genotypes with different growth habits were produced through introgression of allelic variations that affect the plants growth habit, in the genetic background of the tomato cultivar Micro-Tom (MT). The characterization of these genotypes showed that the semi-determinate growth materials exhibit a delay in flowering, producing on average one extra leaf before the first inflorescence formation. In addition, this architecture presents an intermediate height between determinate and indeterminate growth genotypes, 50 days after sowing. As for agronomic traits, we found a significant increase in yield and total soluble solids content (brix) in the fruits of semi-determinate growth genotypes compared with determinate growth. Our data suggest this effect is resulting from a more balanced vegetative and reproductive development, evidenced by the absence of significant difference on the dry matter partition derived from the vegetative and reproductive development in these genotypes, when compared to determinate and indeterminate growth genotypes. WUE was evaluated both gravimetrically (dry mass produced per amount of water transpired), and through isotopic discrimination. The semideterminate growth genotypes showed higher WUE than determinate and indeterminate genotypes at 50 days after sowing. Interestingly, the plants of semideterminate growth were more resistant than determinate growth genotype used as control, when exposed to drought stress. However, studies are needed to elucidate the mechanism involved in this resistance. In conclusion, the results presented here suggest that the genotypes of semi-determinate growth reached the optimal balance between vegetative and reproductive development, in order to increase concomitantly, productivity, brix content in the fruits, and WUE.

À travers la biographie intellectuelle d’un réformateur et rédacteur en chef de Boston, Benjamin O. Flower (1858-1918), de la création de son magazine, The Arena, en 1889 à sa mort, cette thèse explore les ambiguïtés du progressisme et ses « étranges combinaisons théoriques », selon l’expression de l’historien Robert Wiebe. Flower considérait la corruption, la pauvreté et la faillite morale de la société américaine comme des maladies physiques et spirituelles : les idées hétérodoxes de son temps (populisme, socialisme, expérimentations sociales dans le reste du monde mais aussi médecines et spiritualités alternatives) illustraient l’esprit américain de liberté et se révélaient autant de remèdes pour régénérer l’homme et la société. Flower entendait faire de ses magazines une « arène » où débattre librement pour provoquer un nouveau « Grand Réveil » et assurer le progrès de l’humanité. La fin de sa vie voit Flower aux prises avec les ambivalences de sa lutte pour la liberté. Pendant les années 1910, lors de sa croisade pour la « liberté médicale », il lutte contre la volonté de l’American Medical Association de contrôler les médecines alternatives et contre le projet du gouvernement fédéral d’établir un ministère de la Santé. Sa défense de la liberté de la presse face à la censure de la poste le mène ensuite à travailler pendant la Grande Guerre pour un journal anticatholique, The Menace. Ces controverses sur le sens du progrès et de la liberté permettent de comprendre les fractures culturelles qui divisent le réformisme et, à la faveur de l’érection d’un seul et vrai récit de la modernisation, la relégation de son progressisme antimonopolistique dans les marges de l’histoire. / By using as a case study the intellectual biography of Boston reformer and editor Benjamin O. Flower (1858-1918) from the founding of his magazine, The Arena, in 1889 to his death, this dissertation explores the ambiguities of progressivism and revisits its “strange theoretical combinations,” to use historian Robert Wiebe’s phrase. Flower considered the corruption, the poverty and the moral bankruptcy that plagued turn-of-the-century America as physical and spiritual diseases – the nonconformist ideas of his time (populism, socialism, social experiments in the rest of the world, but also alternative medicine and spiritualities) illustrated the American spirit of freedom and could cure and regenerate individuals and society. Flower wanted his magazines, notably the aptly named Arena, to function as an open forum where ideas could be debated freely, thus bringing about a new « Great Awakening » and ensuring progress. At the end of his life, Flower grappled with the ambivalences of freedom. In the 1910s, he fought for “medical freedom,” struggling against the American Medical Association’s move to control alternative medicine and against the creation of a federal Department of Health. He also defended freedom of the press against postal censorship, which led him to work for an anti-Catholic newspaper during the Great War, The Menace. These controversies over the meaning of progress and freedom shed light on the cultural gaps which divided reformism and led to the advent of the modernization narrative and, as a result, to the relegation of antimonopoly progressivism to the margins of history.

Orientador: Leonor Patricia Cerdeira Morellato / Resumo: A visão é o principal sentido utilizado pelos polinizadores para forragear, no qual a cor das flores é a primeira característica de atração. A percepção dos sinais de cores depende da coloração do segundo plano das flores, composto principalmente pelas folhas. Diferenças na composição das espécies e na estrutura da vegetação, e também na sazonalidade climática, podem interferir na cor do segundo plano de folhas em diferentes vegetações e estações, interferindo como os polinizadores percebem a flor. Portanto, a diversidade de cores das flores e os padrões de floração de uma comunidade podem estar relacionados com a composição de polinizadores e condições ambientais. Desta maneira, utilizando comunidades vegetais e considerando o sistema visual das abelhas, nós descrevemos e comparamos a diversidade de cores das flores e seus sinais, dando importância para a cor do segundo plano de folhas em duas vegetações sazonais tropicais e uma vegetação sazonal temperada. Em seguida, para vincular os sinais florais com a sazonalidade, nós analisamos a importância das síndromes de polinização levantadas, o padrão de floração, a influência da cor do segundo plano de folhas no padrão de cor das flores entre as estações. Nós encontramos diferenças na diversidade de cores das flores e confirmamos a influência da coloração do segundo plano de folhas, juntamente com a estrutura da vegetação e a intensidade da sazonalidade nos sinais florais exibidos em diferentes vegetações sazonais, de acordo co... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Vision is the main sense used to forage by pollinators being the flower colour the primary feature of attraction. Colour signals perception depend on the flower background colouration, mainly composed by leaves. Differences in species composition and vegetation structure, and also the seasonality, may change the leaf-background colouration of different vegetations and seasons, interfering how the pollinators perceive a flower. Therefore, flower colour diversity and flowering patterns of a community may be related to the pollinators’ composition and environmental conditions. Using a community level-approach and according to bee visual system, we described and compared the flower colour diversity and the signals of a temperate and two tropical seasonal vegetations, considering their leaf background colouration. Then, to link flower signals to seasonality and using the cerrado sensu stricto as a model of seasonal vegetation, we analysed the importance of the surveyed pollination syndromes, the community flowering pattern, flowering patterns according to the colour of flowers and the influence of seasonal changes in the background colouration in the flower colour signals between seasons. We found differences in flower colour diversity and confirmed the influence of the leaf- background colouration, along with the vegetation structure and seasonality intensity, in flower colour signals displayed in different seasonal vegetations according to the colour vision of bees. Higher value... (Complete abstract click electronic access below) / Mestre

The development of plant flowers represents a complex process controlled by numerous mechanisms. The creation of double homozygous mutant of both β subunits (sometimes also referred to as basic transcription factor 3) of nascent polypeptide associated complex in Arabidopsis thaliana (further referred to as nacβ1 nacβ2) caused quite a strong defective phenotype including abnormal number of flower organs, shorter siliques with a reduced seed set, and inferior pollen germination rate together with a lower ovule targeting efficiency. Previously, NAC complex was described to be formed as a heterodimer composed of an α- and β-subunit, which binds ribosome and acts as a chaperone in Saccharomyces cerevisiae. In plants, NACβ is connected to stress tolerance and to plant development as a transcription regulator. However, little is known of NAC heterodimer function in plants. In this thesis, yeast two hybrid system (Y2H) and bimolecular fluorescence complementation (BiFC) assays were used to verify the NAC heterodimer formation in A. thaliana and to establish any potential interaction preferences between both NACβ paralogues and five NACα paralogues. To deepen the understanding about molecular mechanisms behind the nacβ1 nacβ2 phenotype, flower bud transcriptome of the nacβ1 nacβ2 double homozygous mutants...

Master of Science / Department of Entomology / David C. Margolies / James R. Nechols / A two-year greenhouse experiment was conducted to compare the relative effectiveness of biological control versus chemical control for western flower thrips, Frankliniella occidentalis, as a means of reducing the spread of Tomato spotted wilt virus (TSWV) on tomatoes. To compare efficacy of different thrips management tactics for reducing TSWV incidence, tomatoes were subjected to one of three treatments: 1) biological control based on weekly releases of the predatory mite, Amblyseius cucumeris, at a commercially-recommended rate, 2) a single chemical treatment with Conserve®, a spinosad formulation, or 3) no treatment. TSWV was introduced into the greenhouse either by starting with 20% of the crop already infected and releasing non-viruliferous thrips, or by making a single release of viruliferous thrips. Analyses were done among thrips management tactics for each virus introduction method to examine the cumulative number of weeks plants were infected, the weekly proportion of infected plants, and total marketable yield. The effects of different virus introduction methods were also compared. A comparison of virus introduction methods showed that, among all plants, the average number of weeks they were infected by TSWV was significantly lower when virus was introduced through infected plants than by infected thrips. In addition, when virus was introduced by infected thrips, a significantly greater proportion of plants were infected in any given week than when virus was introduced on infected plants. Finally, crop yields were significantly lower when virus was introduced via infected thrips than on infected plants. Among thrips management methods, plants were infected for significantly less time, and the proportion infected was lower in any given week, when biological or chemical control was applied compared to no thrips management. Tomato yields were not affected by thrips management tactic. There was no significant difference between biological and chemical control in the length of time that plants showed symptoms. However, the proportion of infected plants was marginally greater with biological control in weeks 4 and 5 than with chemical control; differences were not significant thereafter. My findings suggest that inundative releases of biological control may provide as adequate a level of protection from TSWV as chemical control in commercial greenhouse tomato crops.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Our planet is in the midst of a biodiversity crisis, with factors such as land transformation, climate change, anthropomorphic disturbance and invasive species acting together to threaten biodiversity. In South Africa, with minimal natural wood resources, commercial forestry is one of the most abundant forms of landscape transformation. However, a third of the land inside many plantations has been set aside for conservation as unplanted remnant grassland patches (RGPs). These areas are subjected to an additional negative impact by invasive alien species, namely Rubus cuneifolius (American bramble), a weed that is particularly problematic in and around forestry plantations in South Africa. The grassland biome of South Africa is extremely diverse and is of vital importance for the ecosystem services it supplies. Despite this, the grassland biome is under threat as this is where much of South Africa’s forestry plantations are located. Driven by anthropomorphic disturbance, pollinators are in decline. Landscape transformation of natural areas for forestry plantations is likely to affect plant-pollinator interactions which will affect ecosystems and biodiversity. However, it is not known to what extent these ecosystems are affected. It is thought that the impact depends on the complexity of the ecosystem in question, and analyses at the network-level provide insights into the robustness of ecosystems in the face of biodiversity loss. Thus, this study evaluates the effect of natural habitat fragmentation and invasion of the alien species, R. cuneifolius, on flower visitation networks of South African grasslands. The study was conducted in the KwaZulu-Natal Midlands within a commercial timber plantation and a neighbouring protected area (PA). Flower-visitor observations were carried out in uninvaded protected areas and RGPs and in protected areas and RGPs invaded by R. cuneifolius. I found that RGPs within commercial forestry plantations successfully decrease the negative effects of land transformation on the grasslands of the KwaZulu-Natal Midlands, and flower visitation network patterns are largely maintained in these habitat fragments. However, within RGPs, invasion by R. cuneifolius affected the composition and the interaction network structure of flower-visitor and plant communities. The fact that there are unplanted areas within commercial forestry plantations is positive for biodiversity conservation in South Africa. Research has indicated that these areas successfully aid in the conservation of biodiversity and ecosystem functioning. Due to the positive influence that RGPs have on conservation in fragmented and transformed landscapes, it is critical that these unplanted areas are retained. However, the effects of bramble invasion are more intense within RGPs than within protected areas, and therefore, it must be a priority to keep these areas undisturbed. R. cuneifolius has been found to have devastating effects on ecosystem function and network structure. It is also a category 1 invasive plant within South Africa, and its removal is required by law. Therefore, the removal of bramble must be a management priority. / AFRIKAANSE OPSOMMING: Ons planeet is in die middel van 'n biodiversiteit krisis, met faktore soos grond transformasie, klimaatsverandering, antropomorfiese versteuring en indringerspesies wat gesamentlik werk om biodiversiteit te bedreig. Suid-Afrika, besit minimale houtbronne. Daarom is kommersiële bosbou een van die mees algemene vorme van landskap transformasie. Tog is 'n derde van die land binne baie plantasies opsy gesit vir bewaring as oorblywende grasveld kolle (OGKs). Hierdie gebiede word ongelukkig blootgestel aan die bykomende negatiewe impak van die uitheemse spesies, Rubus cuneifolius (Amerikaanse steekdoring), wat veral problematies is in en rondom bosbouplantasies. Die grasveldbioom van Suid-Afrika is baie divers en is van kardinale belang vir die ekosisteem dienste wat dit lewer. Ten spyte hiervan, word die grasveldbioom bedreig waar dit op dieselfde areas as die meerderheid van Suid-Afrika se bosbouplantasies geleë is. Antropomorfiese versteuring lui daartoe dat bestuiwergetalle daal. Landskap transformasie vir bosbou plantasies raak dus plant-bestuiwer interaksies, wat ekosisteme en biodiversiteit beïnvloed. Dit is nie bekend tot watter mate hierdie ekosisteme geraak word nie. Daar word vermoed dat die impak af hang van die kompleksiteit van die ekosisteem. Ontledings van ekosisteme op netwerk vlak kan insigte bied oor die robuustheid van hierdie ekosisteme in die aangesig van biodiversiteitverlies. Dus, die studie evalueer die effek van fragmentasie van natuurlike habitatte en inval van die indringer spesie, R. cuneifolius, op blom-besoekings netwerke van Suid-Afrikaanse grasvelde. Hierdie studie is uitgevoer in die KwaZulu-Natal Midlands binne 'n kommersiële hout plantasie en 'n naburige beskermde gebied (BG). Blom-besoeker waarnemings was in BGs en OGKs sonder R. cuneifolius, en in BGs en OGKs met R. cuneifolius uitgevoer. Ek het gevind dat OGKs binne kommersiële bosbouplantasies suksesvol is om die negatiewe uitwerking van land transformasie te verminder, en blom-besoeking netwerk patrone grootliks gehandhaaf word in hierdie habitat fragmente. Egter, binne OGKs, het R. cuneifolius die samestelling en die interaksie netwerk struktuur van blom-besoekers en plant gemeenskappe negatief geraak. Die feit dat OGKs ongeplant gelaat word, is positief vir die bewaring van biodiversiteit in Suid- Afrika. Navorsing dui aan dat hierdie gebiede suksesvol is om te help met die bewaring van biodiversiteit en ekosisteemfunksionering. As gevolg van die positiewe invloed van OGKs op bewaring in gefragmenteerde en omskepte landskappe, is dit krities dat hierdie areas ongeplant bly. Egter, die gevolge van steekdoring inval is meer intens binne OGKs as binne beskermde gebiede, en daarom moet dit 'n prioriteit wees om hierdie gebiede ongestoord te hou. R. cuneifolius se verwoestende uitwerking op ekosisteem funksie en netwerk struktuur was baie duidelik. Dit is ook 'n kategorie 1 indringerplant in Suid-Afrika, en sy verwydering word deur is die wet vereis. Daarom moet die verwydering van steekdoring ‘n bestuursprioriteit wees.